Arc interrupter for electric switches



L. H. MATTHIAS ARC INTERRUPTER FOR ELECTRIC SWITCHES Nov. 13, 1951 2 SHEETS--SHEET 2 Filed Aug. 7, 1947 [RAMA/5W7 MAG/VET INVENTOD wN-H-MMTHIM L ATTOQNEYZJLmQ/% Patented Nov. 13, 1951 Ano INTERRUPTER FOR ELECTRIC SWITCHES Lynn H. Matthias, Fox Point, Wis., assignor to Allen-Bradley Company, Milwaukee, Wis., a corporation of Wisconsin 7 Application August 7, 1947, Serial No. 766,990

My invention relates to are interrupting devices for electric switches and, in particular, to an arrangement of permanent magnets in conjunction with double break contacts. It is an object of my invention to distend the occurring arcs at the switch contacts away and outwardly from the contacts into the ends of a box-like housing which encloses the stationary and movable contacts. It is also an object of my invention to use usual parts of switch gear and to arrange them in a novel form to accomplish an improved result. And, further, it is an object of my invention to provide a switch in which high interrupting capacity is obtained and in which the cost of construction is comparatively low.

Myv invention comprehends a structure in which a'box-like housing encloses two stationary contacts and a movable contact bar to bridge the stationary contacts, and the two end walls of said box each having imbedded therein a permanent magnet abutting a ferro-magnetic base plate which supports the housing.

My invention, its object and its accomplishment in a particular instance is described in the following specification taken in connection with the following drawings:

Fig. 1 is a perspective view of the entire assembly with the cover of the enclosure broken away to better show the switch mechanism; Fig. 2 shows the switch proper in elevation and location of permanent magnets and diagram of flux lines; and Fig. 3 is a plan view of parts as shown in Fig. 2.

Referring to Fig. 1, a box-like housing designated generally by the numeral 8 encloses stationary contacts 5 and the movable contacts 6 carried by bridge bar I. The housing 8 is mounted on a plate 4 which is a material of low magnetic reluctance such as iron or the like. The housing 8 consists of a base I5, top wall 9 and cover II. The top wall 9 is arranged to support the stationary contacts 5 mounted on terminals [4 (see Fig. 2) and the respective brackets ID for connection into an electric circuit. The housing 8 is closed from the front by means of cover II which is held in place by the nut [2 which is threaded on to screw [3 which, in turn, is fastened to plate 4.

Attached to base plate 4 is an electromagnet assembly designated generally as 20, which is made up primarily of fieldpiece 2|, magnet coil 22 and armature 24. At the upper part of the armature is attached a thimble enclosure 25 on which is mounted the bridge bar 1. The thimble is arranged to slide on post 26 and within the 3 Claims. (Cl. 200--'-147) thimble is a spring not shown to provide a resilient contact pressure between stationary and movable contacts '5 and 6, respectively. Permanent magnets 30 are placed against the metal plate 4 and held in position by recesses in the base I5 of the housing 8.

With reference to Figs. 2 and 3, it will be noted that the permanent magnets have opposite po- 'larity at corresponding ends marked N and S respectively and that therefore there is a cross flux indicated by dotted lines 3| directly in the path of the are when the switch is in its open position. As the path of the current is in the form of a U and is traversed by the path of the flux 31 as shown, the arc is distended outwardly away from the contacts toward the side walls of the box-like housing 8. At the lower currents the are is distended toward the side walls as indicated by the arrows 4| by the flux component provided by the permanent magnets. The flux of the permanent magnets is of high value as compared to the flux produced by the current flowing. At the higher currents the flux due to the current flowing is of higher value and the arc is then distended toward the end walls of the chamber as indicated by the arrows 42.

This construction is simple and eflicient in that the permanent magnets are utilized with the already existing base plate 4 to create the are attenuating flux; and also the magnets 30 do not add appreciably to the cost or size of the existing structure. In the test performance of this switch it was noted that at the lower currents the permanent magnet presumably caused are extinction, whereas at the high current values the arc extinction was caused primarily by the magnetic blowout action of the U shape path of the current. The box-like housing encloses the switch parts and its interior surfaces aid extinction of the arc and also the walls of the housing provide a mounting means and a protective means for the permanent magnet.

While this invention has been above described by reference to a specific instance of an embodiment thereof, it is intended that the protection of Letters Patent to be granted hereon be not unnecessarily limited thereby, and that such protection extend to the substance of the advance contained in this disclosure and defined in the claims hereto appended.

What I claim as my invention is as follows:

1. An electric switch comprising two terminals each having mounted at one end thereof a contact, a bridge bar having a contact on each end thereof and movable to connect said stationary high currents by the inherent blowout efiect of the current itself and to extinguish the are at lower currents by the efiect of the permanent magnets.

2. An electric switch comprising two terminal 4 each having mounted at one end thereof a contact, a bridge bar having a contact on each end thereof and movable to connect said stationary contacts into circuit, said movable and stationary contacts with said terminals forming a, U in circuit closed position, a box-like housing enclosing said bridge bar and-stationary contacts, said housing having the side walls in proximity to a pair of stationary and movable contacts, a ferromagnetic plate to support said box-like housing and two bar-like permanent magnets each of which is positioned one in each side wall with one pole abutting said ferro-magnetic plate and the a other pole in the, line joining the junctures of the each having mounted at one end thereof aconmagnetic plate to support said box-like housing and two bar-like permanent magnets each of which is positioned one in each sidewall of said housing with one pole abutting said ferro-magnetic plate and with the other pole in proximity to a pair of stationary and movable contacts, said two bar magnets and said ferro-magnetic plate forming substantially a U-shaped magnet, with the exposed poles having opposite polarity, and said defined structure to extinguish the arc at high currents by the inherent blowout efiect of the current itself and to extinguish the are at lower currents by. the effect of the permanent magnets.

3. An electric switch comprising two terminals stationary and movable contacts, and said defined structure to extinguish the are at high currents by the inherent blowout efiect of the current itself and to extinguish the arc at lower currents by the effect of the permanent magnet.

LYNN H. MATTHIAS.

REFERENCES CITED The following references are of record in the file of this patent:

Matthias Oct. 16, 1945 

